A variable compliance chamber (VCC) is proposed to control pulmonary input impedance during the treatment of pulmonary disease. Pulmonary impedance is related to the total work the right heart must pump against, and it is altered (primarily in the form of decreased compliance) in pulmonary disease and in the implantation of oxygenation assisted devices; this increase in work can lead to right-heart failure. The VCC can be attached to the right-heart or combined with an artificial lung to decrease the impedance seen by the right ventricle. One application of the VCC will be to augment bridge-to-transplant or recovery treatment of patients suffering from primary or secondary pulmonary hypertension. In Phase I, the optimal geometry and material of the compliant chamber were determined, fabrication techniques were developed, the compliance of the chambers were measured, and two methods for varying the compliance of the chamber were developed and characterized in an in vitro circuit. The objective of Phase II is to construct a clinically feasible VCC device, and to demonstrate and fully characterize its application in controlling pulmonary impedance in an in vivo animal model. At Phase II conclusion, manufacturability of the VCC will be defined, and the in vivo performance of the VCC will be thoroughly detailed as both an independent device, and as a device that augments the performance of the MC3 paracorporeal artificial lung (PAL).